The present invention relates to a method and an air-conditioning device for the air-conditioning of an interior compartment of an electrically driven vehicle by way of the heat losses of an electric drive.
Motor vehicles which are operated purely electrically over relatively long periods of travel comprise electric heating devices for heating the interior compartment, because the heat losses of the electric drivetrain, for example of the battery (high-voltage battery), of the electric machine, of the power electronics, of the direct-current/direct-current converter and the like, are not sufficient, in all driving states, to heat the interior compartment of the motor vehicle. An additional electrical heating device of said type requires additional structural space, increases the costs of the motor vehicle, and increases the weight of the motor vehicle.
From DE 10 2012 019 005 A1, it is known to use the heat losses of the electric machine, and the electrical actuation thereof, for heating the interior compartment of a motor vehicle.
EP 1 313 628 B1 discloses the operation of an electric machine of a motor vehicle outside the optimum operating point for the purposes of increasing the waste heat for the temperature control of the interior compartment.
DE 10 2009 043 316 A1 discloses the use of a heat pump arrangement for the temperature control of the interior compartment of a motor vehicle.
The measures proposed in the prior art for the temperature control of the interior compartment of a motor vehicle having an electric drive are not optimal with regard to the overall efficiency.
It is an object of the invention to provide an improved method and an improved air-conditioning device for the temperature control of an interior compartment of a vehicle.
The method according to the invention for the temperature control of an interior compartment of a motor vehicle having an electric drive controls the temperature of the interior compartment by way of a heat pump arrangement having a heating temperature region and having a low-temperature region, wherein the heating temperature region comprises at least one interior compartment heat exchanger which is thermally coupled to the interior compartment, and the low-temperature region comprises an exterior heat exchanger and/or at least one heat exchanger which is arranged on a component of the electric drive. If the method determines that the interior compartment of the motor vehicle is to be temperature-controlled, heating energy of the heating temperature region of the heat pump arrangement is released to the interior compartment of the vehicle. The operating point of the electric drive is varied such that the generation of heat losses in at least one electrical component of the electric drive is controlled, whereby the temperature of the low-temperature region is, in steady-state or quasi-steady-state operation, controlled to a level which ensures that the heat pump arrangement can provide the heating energy. The required heating energy defines the temperature level that should prevail in the low-temperature region of the heat pump arrangement. The required energy level in the low-temperature region of the heat pump arrangement defines the operating point of the electric drive. In other words, if little heating energy is required and/or if the low-temperature region is at a high temperature, the electric drive is operated at an operating point which corresponds to the optimum operating point or which lies in the vicinity thereof. If the low-temperature region is at a temperature too low to generate the heating energy by way of the heat pump arrangement, the electric drive is operated at an operating point which is further remote from the optimum operating point.
In the context of this invention, an optimum operating point refers to an operating point at which the least possible thermal losses are generated in the electric drive and in the components thereof. The control of an electric drive and the selection of a suitable operating point are known to a person skilled in the art, as is the functioning of a heat pump and the configuration of controllers and regulating loops. Thus, for the sake of conciseness, a description of these will be omitted.
The method according to the invention for the temperature control of the interior compartment of the motor vehicle having the electric drive may comprise supplying heat of the heating temperature region of the heat pump to the interior compartment of the vehicle, if it is determined that the interior compartment of the motor vehicle is to be temperature-controlled. If components of the electric drive generate heat losses of a magnitude sufficient for the temperature control of the interior compartment of the motor vehicle, if at least one component of the electric drive is thermally coupled to a low-temperature region of the heat pump, the heat losses of at least one component of the electric drive are dissipated by way of the low-temperature region of the heat pump, wherein the temperature of the low-temperature region lies, in steady-state or quasi-steady-state operation, in the region of the temperature of the surroundings of the motor vehicle. In this way, the losses that arise when the thermal energy obtained from the heat losses is released to the surroundings of the motor vehicle are reduced.
If the components of the electric drive generate heat losses of a magnitude not sufficient for the temperature control of the interior compartment of the motor vehicle, if at least one component of the electric drive is thermally coupled to the low-temperature region of the heat pump, and if the exterior temperature is so high, and/or the air humidity so low, that there is no risk of function-impairing icing occurring in the region of the low-temperature region, the heat losses of at least one component of the electric drive are dissipated by way of the low-temperature region, wherein the temperature of the low-temperature region lies, in steady-state or quasi-steady-state operation, below the temperature of the surroundings of the vehicle. In this way, it is also possible for heat from the surroundings to be utilized for the temperature control of the interior compartment of the motor vehicle. The lower the temperature of the low-temperature region is, the more heat can be extracted from the surroundings. The temperature of the low-temperature region cannot be selected to be arbitrarily low, because otherwise there would be the risk of function-impairing icing in the region of the low-temperature region. Heat can be extracted from the surroundings by way of a low-temperature heat exchanger or exterior heat exchanger which is situated in the low-temperature region of the heat pump arrangement.
If the components of the electric drive generate heat losses of a magnitude not sufficient for the temperature control of the interior compartment of the motor vehicle, if at least one component is thermally coupled to a low-temperature region of a heat pump, and if the exterior temperature is so low, and/or the air humidity so high, that there is the risk of icing occurring in the region of the low-temperature region, the electric drive is actuated outside the optimum operating point such that the generation of heat losses in a first electrical component of the electric drive increases, and the heat losses generated by the first electrical component are dissipated by way of the low-temperature region of the heat pump arrangement. In this way, the temperature of the low-temperature region can be increased to such an extent that no heat or a little heat is absorbed at the exterior heat exchanger. In this way, it can be ensured that no icing occurs in the region of the low-temperature region or exterior heat exchanger, or the icing does not result in a restriction of function.
The method may be configured such that the fluid of the low-temperature region flows through the low-temperature heat exchanger or exterior heat exchanger, which exchanges heat with the exterior air, only when it is sought to extract heat from the surroundings of the motor vehicle. This is the case if the temperature of the fluid in the low-temperature region is lower than the ambient temperature. If the fluid of the low-temperature region does not flow through the low-temperature heat exchanger, icing is avoided, or a situation in which heat is released to the surroundings is avoided.
The electric drive has a battery, an electric machine which is supplied with current from the battery and which drives the motor vehicle, and a drive control device which controls the supply of current from the battery to the electric machine and/or which controls the charging of the battery with current generated by the electric machine. The drive control device may comprise a direct-current/direct-current converter with a multiplicity of power transistors, an intermediate circuit capacitor, plug connectors, lines, a semiconductor actuation means, capacitors, diodes and further passive components.
The heat pump arrangement may be actuated such that the temperature of the cooling medium of the at least one electrical component lies in the range of +/−10 K, preferably in the range of +/−5 K, around the temperature of the surroundings of the motor vehicle.
The method according to the invention has the advantage that the heat pump arrangement can extract heat not only from the at least one electrical component but also from the surroundings, because the temperature of the first electrical component lies in the region of the temperature of the surroundings. The at least one electrical component and the surroundings are thermally coupled to the low-temperature region of the heat pump arrangement. In the presence of a low exterior temperature below or in the vicinity of the freezing point, the temperature of the at least one electrical component can be kept above or slightly below the temperature of the surroundings of the motor vehicle, and it is thus possible for icing of the exterior heat exchanger to be avoided or reduced.
The low-temperature region may involve an evaporation of the fluid or coolant. Heat is extracted from the first electrical component and/or from the surroundings by way of the evaporating coolant or by way of a water-glycol circuit. Alternatively, the heat pump arrangement may release the generated heat directly, by way of an interior compartment heat exchanger, to the air that is conducted into the interior compartment of the vehicle. The heat pump arrangement may release the generated heat by way of a heat exchanger, which is thermally coupled to the heating temperature region, to a heating liquid which is conducted on at least one further heat exchanger which heats air which is conducted into the interior compartment of the vehicle. This arrangement relates to a liquid-liquid heat pump arrangement, wherein the heating temperature region uses a liquid medium, for example a mixture of glycol and water.
During steady-state or quasi-steady-state operation, the temperature of the first electrical component may, without any change of a parameter relating to the electric drive, vary only by an amount lower than a predetermined threshold value. The expression “steady-state or quasi-steady-state operation” corresponds to the thermally settled state. If no parameter, for example load, speed of the vehicle, inclination of the roadway, a control parameter of the electric machine, the trim, etc., is changed, the temperature of the first electrical component remains substantially constant and changes only by the threshold value. The threshold value may amount to up to +/−5 K, preferably up to +/−10 K. The expression “steady-state or quasi-steady-state operation” does not include the change of the temperature of the first electrical component in the event of a change of a parameter.
The method may furthermore comprise the step of monitoring the temperature of the cooling mechanism of the drive control device and the actuation of the electric drive such that the fluctuation of the temperature of the components of the drive control device is lower than a predetermined threshold value. In this way, it can be ensured that temperature fluctuations of the components of the drive control device are avoided, whereby the service life of the components of the drive control device, and of the drive control device as a whole, can be lengthened.
The method may furthermore have the step of providing current by way of the drive control device such that the ratio of the field-forming current id and the torque-forming current iq lies outside the optimum ratio, for the respective operating point, of the field-forming current id and the torque-forming current iq. In particular, the increase of the field-forming current id leads to greater power losses in the electrical components of the drive control device. By applying current which does not have the optimum ratio of the field-forming current id and the torque-forming current iq, both the temperature in the electric machine and the temperature of the components of the drive control device are increased.
The method may furthermore have the steps of actuating a brake of the motor vehicle and actuating the electric drive such that said electric drive is intended to move the motor vehicle. The parking brake supports the torque generated by the electric machine. This aspect of the invention is suitable for preconditioning of the interior compartment or for the heating of the interior compartment during a traffic-induced stoppage of the motor vehicle, for example at a traffic signal.
The method may furthermore have the step of actuating the drive control device such that only a field-forming current id is supplied to the electric machine. The field-forming current id does not contribute to the output of torque by the electric machine. Slight noises are generated because no rotation takes place. As a result of the application of direct current at a standstill, the continuous load capability of the electric machine and of the drive control device decreases. Owing to possible non-uniform heating, temperature sensors of the winding do not detect particularly hot points (hotspot). This step is possible for the preconditioning of the interior compartment when the motor vehicle is at a standstill, or during a traffic-induced stoppage of the motor vehicle.
The method may have the step of actuating the electric drive such that the drive control device actuates the electric machine such that a rotating field is generated in the electric machine without the axle of the electric machine rotating. The frequency of the rotating field may be of such a magnitude that it cannot effect a rotation of the axle of the electric machine, because too low a torque is generated. Said step is suitable for the preconditioning of the interior compartment of the motor vehicle and during a traffic-induced stoppage of the motor vehicle.
According to another aspect of the invention, the electric drive may, if the electric machine and/or the motor vehicle is at a standstill, be actuated such that the drive control device actuates the electric machine such that the electric machine generates a first torque in a first direction and subsequently generates a second torque in a second direction which is opposite to the first direction. The first torque and the second torque do not cause the motor vehicle to move away from the location at which it is situated. In order that no rotational movement of the drive wheel of the motor vehicle occurs, the regulation must rapidly reverse the torque direction. This aspect of the method may be used for the preconditioning of the interior compartment when the motor vehicle is parked or during traffic-induced stoppages. Furthermore, said mode of operation may be used during initial electric travel, that is to say after the vehicle has been parked for a relatively long period of time.
According to a further aspect, the invention comprises the actuation of the electric drive, if the vehicle is moving, such that the drive control device actuates the electric machine such that the electric machine generates a first superposition torque in the first direction and subsequently generates a second superposition torque in the second direction which is opposite to the first direction. The first superposition torque and the second superposition torque are superposed on a rotational movement of the electric machine. The motor vehicle is not accelerated and is not decelerated by the first superposition torque and the second superposition torque. According to a further aspect of the invention, if a gearbox of the motor vehicle is in neutral, such that no torque is transmitted from the electric machine to a drive wheel, the electric drive may be actuated such that the drive control device actuates the electric machine such that the electric machine generates a torque. This aspect of the invention can be used for the preconditioning of the interior compartment and for heating owing to a traffic-induced stoppage.
According to a further aspect of the invention, if the electric machine generates a torque for driving the vehicle, the electric drive can be actuated such that the drive control device supplies to the electric machine a field-forming current id higher than that required for the respective operating point at which the electric machine is operating. Specifically during starting, it is possible for heating to be performed with the maximum possible heating losses for a short time. The additional field-forming current id is superposed on the normal regulation.
According to a further aspect of the invention, if the electric machine generates current, the electric drive can be actuated such that a higher field-forming current id flows from the electric machine to the drive control device.
The invention also relates to a computer program product which, when loaded into a memory of a computer with a processor, carries out the steps of the method described above.
The invention also relates to an air-conditioning device for a motor vehicle having an electric drive which comprises a battery, a power device and an electric machine which is supplied with current from the battery and which drives the vehicle. The air-conditioning device furthermore comprises a heat pump arrangement having a low-temperature region, which is thermally coupled to at least one component of the electric drive and to the surroundings of the motor vehicle by way of an exterior heat exchanger, and having a heating temperature region, which is thermally coupled to the interior compartment of the motor vehicle by way of an interior compartment heat exchanger. The air-conditioning device is designed such that, if it is determined that the interior compartment of the motor vehicle is to be temperature-controlled, said air-conditioning device supplies heating energy of the heating temperature region of the heat pump arrangement to the interior compartment of the motor vehicle and selects the operating point of the electric drive such that the generation of heat losses in at least one electrical component of the electric drive is controlled, whereby the temperature of the low-temperature region is, in steady-state or quasi-steady-state operation, controlled to a level which ensures that the heat pump arrangement can provide the heating energy.
The device may be refined as described above with regard to the method. With regard to the advantages of the air-conditioning device, reference is made to the method.
The air-conditioning device may be designed such that, if the components of the electric drive generate heat losses of a magnitude sufficient for the temperature control of the interior compartment of the motor vehicle, said air-conditioning device dissipates the heat losses of at least one component of the electric drive by way of the low-temperature region of the heat pump arrangement, wherein the temperature of the low-temperature region lies, in steady-state or quasi-steady-state operation, in the region of the temperature of the surroundings of the motor vehicle. If the components of the electric drive generate heat losses of a magnitude not sufficient for the temperature control of the interior compartment of the motor vehicle, and if the exterior temperature is so high, and/or the air humidity so low, that there is no risk of icing occurring in the region of the low-temperature region, the heat losses of at least one component of the electric drive are dissipated by way of the low-temperature region of the heat pump arrangement, wherein the temperature of the low-temperature region lies, in steady-state or quasi-steady-state operation, below the temperature of the surroundings of the motor vehicle.
If the components of the electric drive generate heat losses of a magnitude not sufficient for the temperature control of the interior compartment of the motor vehicle, and if the exterior temperature is so low, and/or the air humidity so high, that there is the risk of icing occurring in the region of the low-temperature region, the electric drive is actuated by the air-conditioning device such that the generation of heat losses in a first electrical component of the electric drive increases. The heat losses generated by the first electrical component are dissipated by way of the low-temperature region of the heat pump arrangement and are subsequently supplied to the interior compartment. Furthermore, in the low-temperature region of the heat pump arrangement, there is situated a low-temperature heat exchanger which is in the form of a heat exchanger and which thermally couples the fluid to the surroundings. It is however also possible for no valves to be provided, and for the heat exchangers to be connected in series. The air-conditioning device may be refined as described above with regard to the method.
The invention also relates to a motor vehicle having the air-conditioning device described above.
The invention will now be discussed with reference to the appended figure, which shows an exemplary and non-restrictive embodiment of the invention, wherein
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.